1. Field of the Invention
The present invention relates to a laser drilling method and apparatus.
2. Description of Related Art
With regard to a drilling method using a laser beam, Japanese Patent Application Publication No. 2004-243404 (JP 2004-243404 A) describes a method for enlarging a hole while performing scanning with a laser beam.
However, in the laser drilling method of a related art, an inclination angle of the hole thus enlarged is 10 degrees at the maximum, and there is a possibility machining cannot be performed when a necessary inclination angle of a hole is larger than that. For example, in a case where an injection port of a fuel injection valve of an injector is machined, it is necessary for an inclination angle of a hole to be 40 degrees at the maximum. However, in the related art, it is difficult to machine such a large inclination angle. Note that, in the laser drilling method in the related art, in a case where the inclination angle of the hole is inclined at 10 degrees or more, it is necessary to use a larger condenser lens for a laser beam, or to shorten a distance from a lens to a workpiece, thereby resulting in that a laser drilling apparatus becomes very expensive.
In the meantime, such a technique to perform drilling by use of a press without using a laser beam is considered, but drilling using a press cannot achieve expected accuracy for a surface roughness of a surface of a hole, so that there is a possibility that the surface of the hole cannot be finished smoothly. For example, in a case where drilling is performed by use of a press on an injection port of a fuel injection valve, there is a possibility that a requested minute surface roughness cannot be satisfied.